Yahoo:

Follow is a new, free navigation app for iOS and Android that allows drivers to take on the role of “leader” or “follower.” The app constantly keeps track of the leader, which means the followers will never have to risk running a red light to catch up or placing a phone call to find out which turn the leader took.

In order to ensure that everyone in the group is on the same page at all times, Follow pings the location of the leader and the followers three times a second. In other words, no matter how fast you’re traveling, you’ll never lose track of another driver. Follow also notes that drivers can turn off tracking at any time, so you won’t have to worry about your privacy being invaded when the trip is over.

I can see this app being very useful for me. In a car, you can just call the other vehicle to find out where they are if you lose them. But, as a motorcyclist who often rides with others, an app like this would be a huge assist in allowing us to keep track of each other.